1. Field of the Invention
The present invention relates to an apparatus and process for joining a tube inserted within another tube in proximity to their respective ends. More particularly, the apparatus and process of the present invention involve the compression and subsequent radial expansion of one or more elastomeric bars slidably lodged within longitudinal slots of a bushing means. The elastomeric bars expand against the inner surface of the first tube at selective points causing selective expansion of the tube wall against the inner surface of the second tube to create a selective interference fit between the wall of the first tube and the wall of the second tube in proximity to their respective ends.
2. Description of the Prior Art
Prior art methods of expanding tubes include the use of metal rollers located inside the tube which move outwardly from a central position as the rollers are mechanically rotated about the central position. Such methods typically expand the tube only in a round shape about the entire circumference of the tube with the final shape of the tube being a concentric circle relative to the starting position of the tube. In my invention, longitudinal zones of expansion are used to mechanically lock the tubes together, while creating non-expanded zones to permit fluids or gases to flow from inside to outside the tubes at the expansion joint between the tubes.
Other prior art such as U.S. Pat. No. 4,109,365 by Tygart involve the compression of hard rubber or polyurethane by piston forces applied from both ends of the tube, thereby making it difficult to expand the tube at great distances from either end of the tube as when an expandable joint is made in tubular piling at the bottom of the ocean. My invention utilizes a compression force applied from only one end of the tube thereby allowing expansion to occur deep within the tube.
U.S. Pat. No. 4,152,821 by Scott teaches a process for joining a plastic pipe to a plastic or metal coupling by compression of a rubber plug against the inner walls of the plastic pipe. My present invention is not limited to the joining of plastic pipe to a coupling, but rather involves the joining of pipe made of any expandable material to a second pipe. In addition, all prior art including U.S. Pat. No. 4,006,619 by Anderson teaches expansion of the first tube entirely about its circumference to create a close fit between the tubes entirely about their circumferences. My invention, on the other hand, teaches expansion of the first tube at selective locations about its circumference to join with a second tube, yet provide passageways for fluids or other materials to pass through the annular spaces between the tubes. For example, these annular spaces between the tubes may be used for the passage of concrete or other cementitious material from inside one section of tube to outside and around the outer surface of a joined section of tube. In addition, the annular spaces may provide passageways for the escape of gases from inside the tubes to the outside atmosphere. Therefore, what is needed and what has been invented is a process and apparatus for expanding to join at least one pair of tubes without the foregoing deficiencies associated with prior art processes and apparatuses.